BM and PB samples at diagnosis were centralized according to a national GIMEMA original study planned with the aim to accurately evaluate biological characteristics at diagnosis and to identify genetic alterations with prognostic relevance and to follow up cases monitoring minimal disease during remission. To allow the adequate collection and sending of samples before starting intensive chemotherapy, all patients received a 5-day pretreatment consisting of hydroxiurea (HU) at the dosage of 2 g/m2/day, also effective for "debulkying" of disease.